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วันเสาร์ที่ 3 เมษายน พ.ศ. 2553

GSM frequency bands

GSM frequency bands or frequency ranges are the cellular frequencies designated by the ITU for the operation of the GSM for mobile phones.

GSM-900, GSM-1800 and EGSM-900
GSM-900 and GSM-1800 are used in most parts of the world: Europe, Middle East, Africa, Oceania and most of Asia. In South and Central America the following countries use the following:

Costa Rica - GSM-1800
Brazil - GSM-850, 900 and 1800
Guatemala - GSM-850, GSM-900 and 1900
El Salvador - GSM-850, GSM-900 and 1900
GSM-900 uses 890–915 MHz to send information from the mobile station to the base station (uplink) and 935–960 MHz for the other direction (downlink), providing 124 RF channels (channel numbers 1 to 124) spaced at 200 kHz. Duplex spacing of 45 MHz is used. Guard bands 100 kHz wide are placed at either end of the range of frequencies

In some countries the GSM-900 band has been extended to cover a larger frequency range. This 'extended GSM', E-GSM, uses 880–915 MHz (uplink) and 925–960 MHz (downlink), adding 50 channels (channel numbers 975 to 1023 and 0) to the original GSM-900 band. The GSM specifications also describe 'railways GSM', GSM-R, which uses 876–915 MHz (uplink) and 921–960 MHz (downlink). Channel numbers 955 to 1023. GSM-R provides additional channels and specialized services for use by railway personnel.

Phones described as having "EGSM" or "EGSM 900" support both the original GSM 900 band and the extended band. Older phones with "GSM 900" may not support EGSM. Most newer phones with "GSM 900" do support EGSM, it is just not listed that way since it is assumed that newer phones support it..

All these variants are included in the GSM-900 specification

GSM-1800 uses 1710–1785 MHz to send information from the mobile station to the base tranceiver station (uplink) and 1805–1880 MHz for the other direction (downlink), providing 374 channels (channel numbers 512 to 885). Duplex spacing is 95 MHz.

GSM-1800 is also called DCS (Digital Cellular Service) in the United Kingdom, while being called PCS in Hong Kong[2] (not to mix up with GSM-1900 which is commonly called PCS in the rest of the world.)

GSM-850 and GSM-1900
GSM-850 and GSM-1900 are used in the United States, Canada, and many other countries in the Americas.

GSM-850 uses 824–849 MHz to send information from the mobile station to the base station (uplink) and 869–894 MHz for the other direction (downlink). Channel numbers are 128 to 251.
GSM-850 is also sometimes called GSM-800 because this frequency range was known as the "800 MHz band" (for simplification) when it was first allocated for AMPS in the United States in 1983.
The term Cellular is sometimes used to describe the 850 MHz band, because the original analog cellular mobile communication system was allocated in this spectrum.
GSM-1900 uses 1850–1910 MHz to send information from the mobile station to the base station (uplink) and 1930–1990 MHz for the other direction (downlink). Channel numbers are 512 to 810.
PCS is the original name in North America for the 1900 MHz band. It is an initialism for Personal Communications Service.

Another less common GSM version is GSM-450[3]. It uses the same band as, and can co-exist with, old analog NMT systems. NMT is a first generation (1G) mobile phone system which was primarily used in Nordic countries, Benelux, Alpine Countries, Eastern Europe and Russia prior to the introduction of GSM. It operates in either 450.4–457.6 MHz paired with 460.4–467.6 MHz (channel numbers 259 to 293), or 478.8–486 MHz paired with 488.8–496 MHz (channel numbers 306 to 340). GSM Association claims one of its around 680 operator-members has a license to operate a GSM 450 network in Tanzania. However, currently all active public operators in Tanzania use GSM 900/1800 MHz. Overall, where the 450 MHz NMT band exists, it either still runs NMT, or its been replaced by CDMA. GSM-450 is a provision, it has not seen commercial deployment.